When we dive in cold waters, my ( ours ) bodies physiological response is to enter bradycardia, my heart rate drops to 40-50 BPM, blood rushes to my vital organs, and blood rushes away from our extremities. This is so that our bodies conserve oxygen while diving.
Anyways, Ive been toying with the idea of the mammalian dive reflex for a while, and i do different breathing excercies ive picked up from Wim Hof over the years. I love the breathing excercies because i use them a lot for swimming ( part of my training regime for MMA fighting ) and i thought that the breathing excercies would help me with my diving.

Anyways, When my body enters a state described by the mammalian drive reflex, i am having a hard time controlling and even distinguishing the PSYCHOLOGICAL response from the physiological response.

What i am about to ask is only for training and safety purposes, but any other explanations or tips and sources of information regarding the mammalian dive reflex will be greatly appreciated.

When i hold my breath for a long time and my body wants oxygen, it will do these little thing i like to describe as "hiccups". Im not too sure it goes away, but i have managed to stay underwater AFTER i started getting the "hiccups" for one minute and forty five seconds.
I could be one hundred perfect wrong, but is the "hiccup" just how my body reacts to me entering bradycardia?
Is that the response that my body has to a low heart rate?

Op: buy a pulse oxy meter and begin experimenting with that. There are actually different 'types' of contractions and triggers, you can learn the difference. Typically bradycardia and vasoconstriction starts as you begin to experience contractions.

Wow that's great. Im not sure if you're being sarcastic but if i die then its on your hands.

Don't do it in the water or while driving or something else dumb like that , just sit on the couch and hold it as long as you can . If you have the will power you will just black out and instantly wake back up ,it's a very strange feeling

I've heard that blacking out once while diving can lead to an increased chance of blacking out again at some point. What do you guys think? And is the same true if you do it on land?

Like the others said, statically holding your breath on land is much different than when in the water. Sometime's I'll kick my legs or move like I'm diving when I'm laying in bed practicing "statics." Kind of reenact those movements I make in the water. Hiccups when I'm spearing don't occur very often since I don't let myself stay down very long unless absolutely necessary to get at a fish so I'm usually up before the first few

P.S. you'll know that the reflex has started to really kick in when you're peeing in your wetsuit every 5 minutes or so.

Some sambas in a controlled environment may happen for competive freedivers in training but anytime a diver has a full BO it usually a symptom of overtraining and if the diver continues at the same pace, BO could be more frequent.

And some divers have physiology that makes them prone to BO but the first BO isn't causing future ones, they're just prone to BO.

But a one time hypoxic BO is not going to make you susceptible to future ones, at least not after you have rested. In the same day of diving you are certainly more susceptible though because of other factors--if you dive in the ocean hard enough to BO, you typically have gone way over your lactic threshold on at least that one dive, may have been diving all day and have gone into ketosis, are likely more mentally stressed, etc, all factors which will increase your body's O2 consumption; the size of your gas tank is shrinking. If you have a BO while spearing you need to call it a day.

Op: buy a pulse oxy meter and begin experimenting with that. There are actually different 'types' of contractions and triggers, you can learn the difference. Typically bradycardia and vasoconstriction starts as you begin to experience contractions.

Don't do it in the water or while driving or something else dumb like that , just sit on the couch and hold it as long as you can . If you have the will power you will just black out and instantly wake back up ,it's a very strange feeling

I've been put to sleep with Gi chokes in Brazilian Jiu Jitsu, with a lapel choke which cuts off blood circulation. I was breathing just fine until I just passed out. I remember being able to see the static you use to see on television screens, and I remember cartoons playing in the back ground. Then I remembered that I was in BJJ class and woke up. It was a pretty cool experience.

I've heard that blacking out once while diving can lead to an increased chance of blacking out again at some point. What do you guys think? And is the same true if you do it on land?

Like the others said, statically holding your breath on land is much different than when in the water. Sometime's I'll kick my legs or move like I'm diving when I'm laying in bed practicing "statics." Kind of reenact those movements I make in the water. Hiccups when I'm spearing don't occur very often since I don't let myself stay down very long unless absolutely necessary to get at a fish so I'm usually up before the first few

P.S. you'll know that the reflex has started to really kick in when you're peeing in your wetsuit every 5 minutes or so.

That's very interesting. I've never heard that there is an increased chance, but it does make sense to a certain extent. That certain extent being psychological.

Some sambas in a controlled environment may happen for competive freedivers in training but anytime a diver has a full BO it usually a symptom of overtraining and if the diver continues at the same pace, BO could be more frequent.

And some divers have physiology that makes them prone to BO but the first BO isn't causing future ones, they're just prone to BO.

But a one time hypoxic BO is not going to make you susceptible to future ones, at least not after you have rested. In the same day of diving you are certainly more susceptible though because of other factors--if you dive in the ocean hard enough to BO, you typically have gone way over your lactic threshold on at least that one dive, may have been diving all day and have gone into ketosis, are likely more mentally stressed, etc, all factors which will increase your body's O2 consumption; the size of your gas tank is shrinking. If you have a BO while spearing you need to call it a day.

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If I blacked out while spearing, I would def call it a day. and then some. Thanks for that info

I've heard that blacking out once while diving can lead to an increased chance of blacking out again at some point. What do you guys think? And is the same true if you do it on land?

Like the others said, statically holding your breath on land is much different than when in the water. Sometime's I'll kick my legs or move like I'm diving when I'm laying in bed practicing "statics." Kind of reenact those movements I make in the water. Hiccups when I'm spearing don't occur very often since I don't let myself stay down very long unless absolutely necessary to get at a fish so I'm usually up before the first few

P.S. you'll know that the reflex has started to really kick in when you're peeing in your wetsuit every 5 minutes or so.